Author Topic: EM Drive Developments - related to space flight applications - Thread 3  (Read 1803214 times)

Offline PaulF

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(...)

 But for us engineer replicators, garage DIY EM Drives will start being built all over the planet.

DIY EMers should view this short youtube vid: [youtube]I2k2g00onL0[/youtube]

Basically, a 2,000 volt transformer then goes into a doubler making the necessary 4,000 volts for a run of the mill magnetron. This is lethal voltage along with the necessary amperage to assure it. Biggest word here is DO NOT use a DVM or analog meter to measure this voltage. Stay away from it. Be very afraid...there's a reason.
Very good point. Add that to the other warnings about magnetrons. The lethal current is considered to be from around 30mA. At 4 kV, your body and especially your skin WILL BE FRIED with a current of over 1.8 Amps! Now the coils to supply a 1 kW magnetron can't sustain that much current but the voltage will probably drop a good deal due to high load in order to sustain the maximum possible current. It's a killer, no doubt. It doesn't matter anymore if it's AC or DC - you're literally thunderstruck or better said, Lightningstruck ;)



May I suggest a subtopic aimed at laying out all dangers associated with the use of bare magnetron emitters or other dangerous high voltage/current/RF emitters? It should be advocated more seriously on this forum than has been till now. But that's just my opinion.
« Last Edit: 05/28/2015 02:51 AM by PaulF »

Online Rodal

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I think my point is being missed for the case of a completely static gas.
I've seen people arguing for a net nonzero force even in this case.
The reason for pointing this out is to make you think.
Point well taken.

It would be very useful to get strong skeptical reviews of Prof.Yang's paper ((translated) page 4 ( http://www.emdrive.com/NWPU2010translation.pdf  ) concerning her equations stating that having a gas/fluid with charged particles inside the EM Drive results in transfer of its momentum to the EM Drive metallic body. 

Just like the great job you did addressing energy conservation.

It seems to me that she also needs to take into account directional attenuation  in order to get a non-zero Poynting vector.

If you have a chance to look at her equations, I'll for one, would appreciate knowing what you think about them   :)
I tried. The formatting of the equations is execrable, but despite that and after reading all of it, and then realising that she was using Maxwell to produce evidence of an asymmetrical force, I knew the entire paper was wrong. The reason it's wrong is because group velocity is being conflated with phase velocity.
Thanks for taking the time to go through her paper.

When I first read it, a long time ago, I stopped reading it once I saw that she was using group velocity that way and that she was neglecting the forces on the side walls.

However, WarpTech brought to our attention that she does that only in the section of the paper titled  "Original idea of the microwave thruster without propellant" where she essentially repeats Shaywer's formulation.   However later on, she does take into account the stresses on the side walls. 

I just used the search function on my Adobe Professional and I could not find her using "group velocity" or "vg"  or "group" anywhere else but the section  "Original idea of the microwave thruster without propellant" or in her conclusions section where she quickly summarizes that the problem could have been approached another way, using group velocity.

Rather, she uses the Finite Element numerical solution of Maxwell's equations and calculates the Maxwell Stress Tensor components.

In her conclusions she states:

Quote
There are two ways to explain this new thrusters, (1) from the Plank’s hypothesis and Einstein’s quantum theory of light, also the theory of microwave to explain the thrust from the thrusters, that is to quantise the injected microwave to the sealed cavity into photons, its travelling speed is the group speed, photons and the thrust cavity wall elastic collision produce the net thrust, (2) From the classic theory of electrodynamics to explain how the thrust is produce by the thrusters, according to the kinetic energy and conservation of momentum of the electromagnetic system within its volume, Maxwell equation and electromagnetic flux density vector can found out the source of the thrust is coming from the integration of the electromagnetic tensor along the surface of the volume

Please note that she uses option #2 and not #1. For option #2 group velocity is not involved.

Could you please point out where else does she use the group velocity? (other than the section "Original idea of the microwave thruster without propellant" and the quick summary in the conclusions dealing with an alternative approach)

Thanks

« Last Edit: 05/28/2015 02:24 AM by Rodal »

Offline WarpTech

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Todd, have you had a chance to read Aquino's (*) paper (  https://hal.archives-ouvertes.fr/hal-01074608/document ) that I mentioned in my prior post ( http://forum.nasaspaceflight.com/index.php?topic=37642.msg1380265#msg1380265 )?

Remember that Shawyer analyzes the EM Drive cavity as two completely disjointed, discontinuous waveguides: One waveguide having the diameter of the Big end and the other waveguide having the diameter of the Small end.

Aquino goes one step further: he considers the Power dissipated at the Small end to be different than the Power dissipated at the Big end (and indeed we know that the power is dissipated unequally at the ends of the real continuous EM Drive).  What do you think of this approach and its consequences as analyzed by Aquino ?

Force = (PowerDissBigEnd*RefrIndexBigEnd - PowerDissSmallEnd*RefrIndexSmallEnd)/c

(...)

(*) I have been made aware that Prof. Aquino has other out of the mainstream physics papers (concerning gravitational vs inertial mass), but the the purpose here is to address these equations solely based on their mathematical physics foundation and validity.

I've always referred to him as De Aquino, so at first I didn't recognize the name. Anyway, he does what he always does. He takes a fairly good idea, makes grandiose claims and then butchers the theory. Without going into detail on how he meanders off into the QV without a clue, I will say he has the right idea about materials. Here's the gist of it;

Forget the Frustum for a moment. Suppose we have a solenoidal coil, say 1 meter long, a few inches in diameter. Say, PVC pipe wrapped in copper wire. It is now an Air Core inductor.

At one end, we plug the opening with a perfectly conducting disk. At the other end, we plug it with a perfect Ferromagnetic disk. As the current through the inductor is charging, imagine the Vector Potential field, "A(x,t), where x is along the length of the solenoid. EM momentum is Q*A, so A(x,t) will be proportional to momentum of the field. As the inductor charges, the "A" field, along with the coil will be pushed backwards, toward the magnetic end and repelled from the conductor end. Likewise, magnetic disk and the conducting disk will be pushed forward, in the same direction, toward the conductive end forward.

The conductive end is a "short circuit" on the coil, a perfect reflector. The magnetic end is an absorber, it stores energy without dissipation. In a system as I've described, even at 60Hz, the forces are not trivial. Failure of those forces to perfectly cancel each other out, may lead to a significant "thrust" without propellant.

Todd
 


Offline TheTraveller

Calculating Shawyer Demonstrator Df.

Shawyer's thrust equation T = (2 * Df * Po * Q) / c gives us the ability to calc Df, knowing Q, T & Po as Df = (c * T) / (2 * Po * Q)

Demonstrator EM Drive, published data:

Q: 45,000
Po: 334W
T: 0.096N

Therefore Df = 0.95714. This suggests Shawyer's reported Df of 0.844 is correct as effective Q at measured power may not be 45,000 due to thermal detuning or the magnetron frequency not being at cavity resonance.

When calculating the small end diameter, we must know the TEm,n or TMm,n excitation mode as the cutoff wavelength can vary quite a lot, which effects guide wavelengths Lambda g1 and Lambda g2 and thus Df. As we don't the mode, we must assume the Df of 0.844 is the correct value. A bit of playing with modes and trying different small end values may reveal the mode and true small end size.

Have fun.
« Last Edit: 05/28/2015 02:38 AM by TheTraveller »
"As for me, I am tormented with an everlasting itch for things remote. I love to sail forbidden seas.”
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Offline deltaMass

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Quote from: WarpTech
The conductive end is a "short circuit" on the coil, a perfect reflector. The magnetic end is an absorber, it stores energy without dissipation. In a system as I've described, even at 60Hz, the forces are not trivial. Failure of those forces to perfectly cancel each other out, may lead to a significant "thrust" without propellant.
Why don't you build it and find out?

When you discover it doesn't work, you'll be a better theorist for the experience, because you will first have to discover and understand your error, and then you will never again repeat it.
« Last Edit: 05/28/2015 02:41 AM by deltaMass »

Online Rodal

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Calculating Shawyer Demonstrator Df.

Shawyer's thrust equation T = (2 * Df * Po * Q) / c gives us the ability to calc Df, knowing Q, T & Po as Df = (c * T) / (2 * Po * Q)

Demonstrator EM Drive, published data:

Q: 45,000
Po: 334W
T: 0.096N

Therefore Df = 0.95714. This suggests Shawyer's reported Df of 0.844 is correct as effective Q at measured power may not be 45,000 due to thermal detuning or the magnetron frequency not being at cavity resonance.

...

The big problem with inverting any multivariable equation like Shawyer's equation where T is an unknown :

to get Df = (c * T) / (2 * Po * Q)

in terms of experimental values, is that such an inversion presumes that Df is a free parameter that can be forced to give any value of experimental value of thrust (*)

One could do that with any equation, we could put a free parameter in McCulloch's equations for example and match a given set of experimental values as well.

So, the right way to do this is not that way, but instead to have an expression for Df in terms of the geometry, and compute Df from the geometry, and then compare the predicted value of thrust force to experiments.

The problem is that using Df = 0.95714 gives a diameter for the small base that is way smaller than what the Demo picture shows, as previously discussed in this thread by @phaseshift, when using the lowest possible mode shape as the cut-off frequency. 

If the Design Factor is not expressed in terms of a defined cut-off frequency (like the lowest possible cut-off frequency) as we did in the previous pages, then the Design Factor is not a well-posed equation until it is defined what mode shape one is supposed to use for the cut-off frequency in the Design Factor.

As you said, then one can "have fun"

________

(*) I could write  an equation like this

PriceOfIBM[@9:30am] = temperature[@9:30am] * Df

now, give me the temperature at a future day and the PriceOfIBM@9:30 that future day, and I can calculate Df ( $/share per deg C), so as to give the price of IBM exactly. 

Does that give me a value of Df that then I can use to predict the price of IBM stock the following day ? Of course not. The problem is that you are presuming that Shawyer's equation with an independently calculated Df prior to an experiment can predict the value of thrust you are going to get in all future experiments, for any value of P, Q and any geometry.
« Last Edit: 05/28/2015 03:05 AM by Rodal »

Offline deltaMass

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Two comments: a) nothing here is worth more than 2 or 3 digits of precision, and b) Df does serve at least the purpose of bounding the thrust from above at the limiting value given by Df = 1.
« Last Edit: 05/28/2015 02:44 AM by deltaMass »

Offline TheTraveller

Calculating Shawyer Demonstrator Df.

Shawyer's thrust equation T = (2 * Df * Po * Q) / c gives us the ability to calc Df, knowing Q, T & Po as Df = (c * T) / (2 * Po * Q)

Demonstrator EM Drive, published data:

Q: 45,000
Po: 334W
T: 0.096N

Therefore Df = 0.95714. This suggests Shawyer's reported Df of 0.844 is correct as effective Q at measured power may not be 45,000 due to thermal detuning or the magnetron frequency not being at cavity resonance.

...

The big problem with inverting any multivariable equation like Shawyer's equation where T is an unknown :

to get Df = (c * T) / (2 * Po * Q)

in terms of experimental values, is that such an inversion presumes that Shawyer's equation can accurately predict experimental values to that level of accuracy.

In other words, Df is a free parameter that can be forced to give any value of experimental value of thrust.

One could do that with any equation, we could put a free parameter in McCulloch's equations for example and match a given set of experimental values as well.

So, the right way to do this is not that way, but instead to have an expression for Df in terms of the geometry, and compute Df from the geometry, and then compare the predicted value of thrust force to experiments.

The problem is that using Df = 0.95714 gives a diameter for the small base that is way smaller than what the Demo picture shows, as previously discussed in this thread by phase-shift

Df is affected by the guide wavelength,  which is affected by the cut-off wavelength, which is affected by both the diameter and the excitation mode.

If we don't know the excitation mode, we can't use the Df to reverse calc the small end diameter from the big.

Shawyer used 0.844 as the Demonstrator Df in many papers. I suggest it is correct.

Using the same Df calc method I get similar high Dfs for the Flight Thruster so I expect it's Df to also be high. There we know the excitation mode is TE013 & so can cross check with a forward Df calc as we know,  sort of, the internal dimensions.

I'll have more data on the Flight Thruster in a few days. Hopefully enough to place a laser cut order for the frustum.
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Offline TheTraveller

If the Design Factor is not expressed in terms of a defined cut-off frequency (like the lowest possible cut-off frequency) as we did in the previous pages, then the Design Factor is not a well-posed equation until it is defined what mode shape one is supposed to use for the cut-off frequency in the Design Factor.

As you said, then one can "have fun"

You can't calc guide wavelength, the basic of the Df equation, without knowing cut off wavelength, which depends on diameter and excitation mode. Excitation mode is at the heart of the Df equation, via its affect on cut off wavelength.

Without knowing excitation mode, doing reverse end plate sizes from the other end plate and Df is fruitless, unless you are on a fishing trip.
« Last Edit: 05/28/2015 03:04 AM by TheTraveller »
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Offline deltaMass

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From which we conclude, because 0 <= Df <= 1, that
0 <= F <= 2 Q P/c , where F is the thrust.

So with Df = 1 and even if Q =1, F is twice that which would be delivered by a photon rocket at power P. Sound right to you?


Offline Blaine

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i just looked at a critique based on the bayes outlook of emdrive and i can only say...bayes theorem is the dumbest thing i have ever heard of in my life.  i understand the math just fine.  its just so hand wavy abd full of hot air that i cant take the critism seriously at all.
Weird Science!

Offline WarpTech

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Quote from: WarpTech
The conductive end is a "short circuit" on the coil, a perfect reflector. The magnetic end is an absorber, it stores energy without dissipation. In a system as I've described, even at 60Hz, the forces are not trivial. Failure of those forces to perfectly cancel each other out, may lead to a significant "thrust" without propellant.
Why don't you build it and find out?

When you discover it doesn't work, you'll be a better theorist for the experience, because you will first have to discover and understand your error, and then you will never again repeat it.

First off, Yang's final equation for force is correct. She integrates the E and B pressures over all surfaces. She does not use group velocity, or phase velocity, but I did see the error you are referring to. It is irrelevant to the end result. Please show us the error? Maxwell's equations can predict the thrust perfectly well, if dissipation, attenuation, reflection, absorption and scattering are ALL taken into consideration accurately. Nobody has done that yet, but Yang's equation is the best approach if you have the software to crunch the integrals. Just plug in values of E and B that have amplitudes, phases, frequencies and time dependence on these factors, at all coordinates on the surface. Piece of cake! ;)

Given a system of 2 diametrically opposing forces, and all the variables we have at our disposal. Can we create a system that when it is charging or discharging, is mechanically off-balance and propagates forward? I already know this can be done, has been done and is being done because dissipative systems are not conservative. What remains to be determined is, how "should" we calculate it as engineers and how do we optimize it? Yang said;

Quote

The thrust curves demonstrate that on the surfaces of the ma- jor and the minor end plates, the magnetic thrust is two orders of magnitude higher than the electric thrust; on the surface of the side wall, the magnetic thrust is three times of the electric thrust;



This says the imbalance on just the end plates is 100X more significant than those on the sidewalls. So my thought experiment is optimizing that end of it, so to speak.  ;D

Maybe I will build one and test it, but I have 50 some odd solar projects to manage at the moment and no spare change. My spare time is mostly spent here, trying to keep up. LOL!
« Last Edit: 05/28/2015 03:30 AM by WarpTech »

Offline deltaMass

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OK on the time issues! But my point is that no application of Maxwell, dissipative or not, should result in thrust greater than a photon rocket. Maxwell's stress tensor is well understood and if a calculation using it produces a thrust value greater than a photon rocket, then a mistake has been made. It is possible to say that with absolute certainty without actually identifying the error.

Furthermore, your mark-space ratio idea on Q*P with a duty cycle of 1:Q won't save you. You will also measure a time-averaged thrust value that is on order P/c, so everything comes out right. It does not explain how a time-averaged thrust of Q*P could be measured.
« Last Edit: 05/28/2015 03:49 AM by deltaMass »

Offline zen-in

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I...
Point well taken.

It would be very useful to get strong skeptical reviews of Prof.Yang's paper ((translated) page 4 ( http://www.emdrive.com/NWPU2010translation.pdf  ) concerning her equations stating that having a gas/fluid with charged particles inside the EM Drive results in transfer of its momentum to the EM Drive metallic body. 
...

I was under the impression that Yang had built an EM drive and had done a series of experiments that showed it could produce a mN thrust.   There is no mention of any experiments or measurements in the above translated paper.   I'll have to tip my hat to whoever translated it.   A well done job.

So this is the problem I have with believing the EM-drive is not a hoax; or stated more politely a case of mistaken measurements.    In thread 2 I stated the EW thrust signatures were not consistent with the known step response of their torque pendulum.   The calibration pulse, generated by a capacitive device, always produced an underdamped response (thrust graph).   This is the response that anything that pushes on the cavity should produce.   If a moth flew at the cavity, this same step response would be seen.   This is an immutable physical observation of mechanical systems.  They all have a natural frequency and a damping coefficient.   Any perturbation will exhibit the same step response.    However the EW thrust signatures when the RF power was turned on were completely different.   From this observation it can be concluded the RF power is not producing thrust.   

Others have offered alternative explanations for the apparent movement when RF power is applied.   Since we are talking about only 4-5 microns of apparent movement there can be many alternative, conventional explanations.

All the essays describing these experiments (EW, Shawyer, and now Yang) make a lot of claims but show very little data.    Shawyer has been doing this since 2003 and yet his raw data has never been released.   EW has released a few graphs but one can assume that given the amount of time they have been experimenting there is a lot more data.   So have they cherry-picked the data and just shown us the graphs that appear to show thrust?   If so that would indicate a very low percentage of possibly "good" tests.

In Monday's new York Times (pages A1, A11  "Maligned study..") there is a piece on a paper that the journal Science is considering retracting.   One of the authors has his hopes set on a "dream job" as a professor at Princeton.  However his faculty  advisor has asked Science to retract the paper because the author "... had misrepresented his study methods and lacked the evidence to back up his findings."  (quoted from NYT article)  The author was asked several times to make his raw data available in case his work needed to be checked, but never did.

It is one thing to say you have a propellantless microwave thruster and that in a few years cars will be flying but if there is no data to support these claims any sane individual would have to say it has all been a hoax.

So to all you DIY'ers out there: Don't electrocute yourself or give yourself cataracts, etc., chasing a dream that will never materialize.
« Last Edit: 05/28/2015 06:21 AM by zen-in »

Offline Star One

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I found this on another site it maybe of relevance to this topic. It's a new scientific paper.

Theory of everything? How spacetime is built by quantum entanglement

http://www.sciencedaily.com/releases/2015/05/150527112953.htm


Offline ThinkerX

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Quote
It is one thing to say you have a propellantless microwave thruster and that in a few years cars will be flying but if there is no data to support these claims any sane individual would have to say it has all been a hoax.

So to all you DIY'ers out there: Don't electrocute yourself or give yourself cataracts, etc., chasing a dream that will never materialize.

Expressing skepticism is one thing.  Discouraging independent investigation is something else.

And I stand squarely on the fence with this device - the theories and experiments all have problems, yet there is just enough in the way of ambiguous or positive results to warrant further investigation. 

Offline Stormbringer

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so, no scat, there i was... I learned you can do stuff that violates the laws of physics so long as you label the process as happening in imaginary time even if it has real physical consequences.

http://phys.org/news/2015-05-physicists-quantum-tunneling-mystery.html

Synopsis: Massive things that quantum tunnel can violate the physical speed limit of light so long as there isn't anybody watching and there cannot be anyone watching because it happens in imaginary time.

I don't know about you; but i kind of had a different idea of what "imaginary" means but evidently imaginary does NOT mean unreal.

« Last Edit: 05/28/2015 07:20 AM by Stormbringer »
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Offline Flyby

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This says the imbalance on just the end plates is 100X more significant than those on the sidewalls. So my thought experiment is optimizing that end of it, so to speak.  ;D


On condition of course that it is really the case, wouldn't it make sense then to use "metglas" on the (small?) endplate, because it has a dramatically increased magnetic permeability, compared to copper?(x1000000)
Wouldn't that greatly amplify that magnetic imbalance then?

http://en.wikipedia.org/wiki/Permeability_%28electromagnetism%29

It was talked about some 150 pages ago or so, but it fell between the cracks...

IF we assume that the EMdrive gets validated as a thrust generating device, I think we should try to setup some experimental parameters that will test each of the proposed theories on their validity.
Maybe we should setup a listing of the proposed theories/conjectures we got so far and how we could experimentally test them individually? if they fail, you can scrap the theory and move to the next one...

Offline Star One

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so, no scat, there i was... I learned you can do stuff that violates the laws of physics so long as you label the process as happening in imaginary time even if it has real physical consequences.

http://phys.org/news/2015-05-physicists-quantum-tunneling-mystery.html

Synopsis: Massive things that quantum tunnel can violate the physical speed limit of light so long as there isn't anybody watching and there cannot be anyone watching because it happens in imaginary time.

I don't know about you; but i kind of had a different idea of what "imaginary" means but evidently imaginary does NOT mean unreal.

Isn't that the same thing as I just posted above but with a different spin, if you pardon the pun?

I saw someone suggesting & no idea if it's correct that this allows theoretical for greater than speed of light & teleportation?

Offline Stormbringer

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so, no scat, there i was... I learned you can do stuff that violates the laws of physics so long as you label the process as happening in imaginary time even if it has real physical consequences.

http://phys.org/news/2015-05-physicists-quantum-tunneling-mystery.html

Synopsis: Massive things that quantum tunnel can violate the physical speed limit of light so long as there isn't anybody watching and there cannot be anyone watching because it happens in imaginary time.

I don't know about you; but i kind of had a different idea of what "imaginary" means but evidently imaginary does NOT mean unreal.

Isn't that the same thing as I just posted above but with a different spin, if you pardon the pun?

I saw someone suggesting & no idea if it's correct that this allows theoretical for greater than speed of light & teleportation?

It may just be the articles treatment of the underlying paper but but i do not take it as being the same thing as your post. But really a half a year  to  a year ago there were a couple of articles on entanglement and wormholes and gravity all being related in the manner you suggest. In my case the thing was quantum tunneling of a massive object being instantaneous and thus implying FTL travel albeit in "imaginary" time. :)
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